Automatic firearm



June 27, 1944. W, T, GQRTON 2,352,193

AUTOMATIC FIREARM Filed Aug. 7, 1942 Patented June 27, 1944 l UNITED STATES PATENT oFFlcE (Granted under the act OfMarch 3, v1.883, as amended April 30,1928; 370 O. G. 757).

2' Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to an improved bolt operating mechanism for an automatic rearm having a recoiling barrel.

Itis an object of this invention to provide a bolt operating mechanism for an automaticflrearm utilizing recoil and blow-back forces consecutively to obtain unlocking and opening of the bolt.

Another object oi this invention is to provide a firearm bolt with a locking member which engages a suitable stop or shoulder on a xed member attached to a barrel.

Another object of this invention is to provide a firearm having a short recoil movement of the barrel wherein the bolt is maintained in locked relation therewith during the initial recoil 1 movement.

It is a further object of this invention to provide means for releasing the bolt locking member from its locked relation with the barrel by the recoil movement thereof thereby permitting the bolt to be opened by blow back action of the residuall gas pressure.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description oi a preferred embodiment as shown in the accompanying drawing in which:

Fig. 1 is a sectionalized view of the assembled operating mechanism for a firearm. In this View the moving parts of the mechanism are shown at the position of extreme recoil movement of the bolt.

Fig. 2 is a view similar to Fig. 1 however with the movable parts shown in their positions immediately after the pulling of the trigger.

Fig. 3 is a sectional View taken along the plane 3-3 of Fig. 2.

As shown in Fig. 1, in assembled relation, a barrel I is fixedly secured to a barrel extension 2, preferably by threads Ia. The barrel extension 2 shown in its preferred form is a long narrow rectangular member with rounded exterior corners. Longitudinal grooves 3 and 3a (Fig. 3) provided on the inside of the barrel extension 2,

lnear the lower edge of the extension, slidably engage the ribs 4 and 4a of a receiver 5, which is not shown in detail but may be of any suitable conventional structure.

Provision is made Within the extension 2 for housing a rectangular bolt IS. The bolt E is slidably supported within the barrel extension 2 by the receiver E'andis guided therein by ribs 1 and la oi receiver 5, which engage suitable grooves in the bottom of bolt 6. In the bolt 6' a firing pin 9 is mounted for longitudinal movement within the axial ring. pin hole 8 provided in bolt 6.

l A iiring pin spring II) surrounds the iiring pin S and a retaining nut II holds the iiring pin and spring within the ring pin hole 8'. A bolt lock I2, preferably in the. form of a rectangular bar, is hinged within a suitable recess` in the bolt E by a transverse pin I3 which passes thru the hole I3a in bolt lock I2 and a suitable holev 6a in the bolt. 'I'he hinged end ofthe bolt lock I2' is formed as a semi-circular surface I2c having the transverse hole I3a. as a center. This hinged end oi the bolt lock ts snugly in a correspondingly shaped recess I'3ci'rr the bolt G. Theother end IZa of the bolt lock I2 projects beyond the end of bolt 6 for a purpose to be described. A weak spring 46 is inserted between the bolt lock I2 and the bolt 6 in suitable recesses 46a and 4Gb in the bolt lock I2 and bolt 6 respectively. rlhis spring 46 exerts an upward force on bolt lock I2 and, in the closed `position of the b'olt 6, urges the bolt lock I2 into a correspondingly `shaped recess 2I' provided within the barrel .extension 2. The end surface 21a of the bolt lock recess 2l is iormedat. such an angle as to provide positive locking of the. bolt to 'the' barrel extension when the bolt lock I2 is held up in bolt lock recess 2| by a bolt lock support 22 tov be described later and yet to tend to camrb'olt lock I2 out of locked engagement when bolt 6 .isV forced rearwardly with respect to barrel extension 2'. The projecting end I2a ofthe bolt lock is shaped to correspond to the face 2I1a.` of-r recess 2 IV in barrel extension 2, so that. when the bolt lock I2 is raised into the recess 2I the end` or face. I2a will snugly engage the facev 21a of therecess' 2 I', and the face 4U of bolt` Ei will be' the proper distance from the end 4I' of barrel I. This distance iscommonly known as headspace; The lower corner I2b of bolt lock I2` is rounded' to provide al suitable cam surface which assists in'- raising the bolt lock I2 into the recess 2l by Gamm-ing action of a bolt lock support 22, ashereafter described.

As already stated the barrel extension 2 with barrel I` secured? theretois slidably mounted on the receiver 5, the grooves 3 and 3'ain the barrel extension 2 engaging the ribs 4 and 4`of the receiver. A bracket member I'4ts snugly around the barrel I, abutting a shoulder I5 on barrel I, and is securely held between the shoulder I`5 on barrel I and barrel extension 2. An integral,

downwardly projecting lug I4a on the member I4 is provided with a suitable hole |417 which is engaged bye. bolt I6 which bolt is secured to the receiver by threads 20. A head I9 on the returns the barrel I and barrel extension 2 to.V

the forward position as shown in Fig. 2 after 1 j vmitted through the bolt lock I2 to the shoulder their recoil movement has been completed. j@ L.

A bolt lock support 22 is provided to assist in raising the bolt lock I2 to the locked"pos`,itionv` and to secure it therein. The boltlock support 22 is a slotted member the lower end of which is hinged about a transverse pin 23, the pin 23 i passing thru suitable holes in the support 22 and the receiver 5. The upper 'endof support '22.is rounded to a radius having the pin 23 as center, as shown at 22c, so as to continue to support the bolt lock I2 evenrwhenpivoted slightly counterclockwise about pin 23. A U-shaped torsion spring 24is looped around pin 23 and the free ends inserted Ain suitable holes 25a,` and 25h in housing 5. The closed end. of torsion spring 24 bears against the upper rear surface of support 22 biasing support A22 clockwise into an upright position. The rear face of bolt 6 acts as the ystop-for the suppont 22 when the bolt is in itsclosed position. Hence the support 22 acts somewhat asa follower with respect to the bolt.

A preferred form of bolt lock support and hammer is shown inFig. 3 wherein the support .is

slotted to form two forklike members 22a andf22b. l The slot formed by the forks22a and 22h surrounds a hammer 26, which is pivotally mounted on the pin 23, and is of suitable shape to pass thru Athe slot formed by members 22a and 22h of member 22. YOne end of` a hammer spring 28 vis suitably attached rto hammer 26.

` The other end of hammer spring 28 is supported on a con- `ven'tional hammer spring strut 29. The hammer spring strut 29 is pivotally mounted on a transvverse pin 30, which is mounted in the receiver.

5.` A sear notch 3l is provided on-.the bottom Aof. hammer 26 to engage a sear 32 when the hammer is in the cocked position.

From the recoiled position the bolt 6 is rey.turned to its forward position as shown in Fig. 2

by compressed operating spring 33,one end of which is inserted in a suitable recess in the rear ofbolt 6 (not shown), while the other end slides over a guide rod 34. The guide rod 34 passes thru a suitable hole 35 in the rear of barrel4 extension 2l and extends into the extension 2 `only a sulicient distance to properly supportthe driving spring 23. The-guide rod 34 is secured within the extension 2 by the pin 36 which locks .in a suitable recess when the rod 34 is turned approximately a quarter turn in either direction.

A bolthandle 31, comprising a knurled cylindrical `portion 31a, which can be conveniently .grasped vbythe fingers, and an integral straight shaft vsection 31h projecting inwardlyl therefrom,\` thru a suitable longitudinal slot in the barrel extension 2, (not shown) and into a suitable recess 6b in the bolt 6, i-s provided for manual operation of thebolt. The bolt handle 31 is secured within the longitudinal slot by any conventionall ,means- *Firing is effected whenthe/sear 32 is released from engagement with the sear notch 3I of hammer 26 by a conventional trigger mechanism (not shown) and the hammer. under the action ofa `barrel extension 2 as theb'olt closes. assisted 'by of the bolt lock I2.

-ment of the bolt lock O 4,mer 26, thus stressing the bolt lock support spring 5` 32 in sear notch 3| is also effected. Y The rear- I2 contacts shoulder `barrel. extension the projection cured between the barrel and "Vagainstrshoulder I 'I of bolt Aand barrel extension are hammer spring 28, strikes firing pin 9 and assumes the position shown in Fig. 2. The for- Ward movement of the ring pin 9 caused by the hammer blow discharges a cartridge 38 in chamber 39 of barrel I. The resultingexplosion exerts a tremendous rearward pressure against the face 40 ofv bolt 6.y However, shown in Fig. 1 the bolt lock I 2 is in the locked position and so held there by the bolt lock" support "22. It is readily discernible that the rearward thrust caused by the discharge of the cartridge is trans- 2I of the barrel extension 2, thus causing a rearward movement of barrel extension 2 and barrel I2 along the ribs 4 and 4a of housing 5. As the breech pressure at the moment of discharge of a cartridge in a firearm of the type herein l described is exceedingly high, it is vitally necessary to maintain lthe bolt in locked relation with the barrel until the pressure in the chamber has vbeen substantially reduced. Thereafter vthe bolt 6 is maintained in locked relation with the barvrel extension 2 until vthe barrel extension 2 and barrel I recoil a predetermined distance,;thus

.pivoting bolt lock support 22 slightlycount'erclockwise. By this time the pressure in chamber 39 has been appreciably 4reduced by the passage of thel bullet 44 along the `bore 43 of barrel I to .a point where V- safe unlocking of the boltcan ,be effected. 'I'he initialrecoilmovement ofthe barrel extension 2 and barrel I alsostarteda counter-clockwise rotational movement of the hammer 26 about the pin 23. The slight counterclockwise rotation of the bolt lock supporting member 22 result'sin withdrawal of positive support for the bolt lock I 2. ,y The residual pressure on the face of the bolt vis still of considerable rmagnitude and by the camming action between surfaces 2Ia. of the barrel extension vand I2a of the bolt lock the bolt lock I2I is forced down'-` ward and out of engagement with the shoulder 2 Ia of the barrel extension 2, thus unlocking the Vbolt and permitting it lto fly backwards under the force of the gases. The bolt lock spring 461s lof course compressed by the downward movement 4The continued rearward travel of the bolt causes further rotational movesupport 22 and the ham# 24 and .hammer spring 28.v Engagement of sea-r During the recoil AFig. 2.

As the bolt 6 passes overrthebolt lock sup--V portl 22 the bias of spring 24 forces the support 22 to follow the bolt. The spring 46l biases the bolt lock I2 upwards into` the recess 2km-"the thehcamminrg action of bolt lock y supportV surface 22e on bolt lock surface I2b.,vSupport'22.rests .against the rear of therbolt, 6 andI fully supports the boltulock I2. thus locking thebolt m'echa'riisrn to the barrel ready for the discharge of another cartridge.

The rifle described herein can readily be converted to continuous automatic re as well as semi-automatic fire by the use of any suitable conventional trigger mechanism (not shown) whereby at will the Sear 32 can be held depressed and out of engagement with the sear notch 3| after the discharge of the rst cartridge, thereby allowing the hammer to follow the bolt on the closing stroke and automatically re the succeeding cartridge. Release of the trigger permits the sear 32 to engage the sear notch 3l which holds the hammer 26 in the cocked position and prevents the discharge of another cartridge thereby causing the rifle to stop firing.

It should be understoodrthat extraction and ejection of the previous empty cartridge case can be eiected during the rearward movement of the bolt by any conventional extractor and ejector (not shown) provided on the bolt head. Feeding a new cartridge into the chamber 39 oi barrel I is accomplished by the face 40 of bolt 6 picking up a cartridge from a conventional magazine (not shown) in the magazine well 41 and pushing it into the chamber 39 on the closing stroke of the bolt 6.

I claim:

1. An automatic firearm comprising a receiver, a barrel, a hollow extension secured to said barrel and mounted on said receiver for reciprocal movement, resilient means resisting rearward movement of the barrel with respect to the receiver, a bolt mounted on said receiver for independent reciprocal movement within said barrel extension, a firing pin mounted within said bolt and extending to the rear of the bolt, resilient means resisting rearward movement of the bolt, a rearwardly projecting latch pivotally secured to the top of said bolt, a latching surface on said barrel extension engageable by said latch when the bolt is in battery position, a hammer pivotally mounted in said receiver beneath the bolt and adapted to engage the rear of the ring pin when the bolt is in battery position, a bifurcated follower surrounding said hammer and pivotally mounted to the receiver, said follower adapted to engage said latch when the bolt is in battery position to hold the latch in engagement with said latching surface thereby locking the bolt to the barrel until the barrel recoils a substantial distance with respect to the receiver, and resilient means biasing said follower forwardly.

2. An automatic rearm comprising a receiver, a. barrel, a hollow extension secured to said barrel and mounted on said receiver for reciprocal movement, resilient means resisting rearward movement of the barrel with respect to the receiver, a bolt mounted on said receiver for independent reciprocal movement within said bei rel extension, a ring pin mounted within said bolt and extending to the rear of the bolt, re silient means resisting rearward movement oi the bolt, a longitudinal recess in the top of the bolt, a latch mounted in the recess having its forward end pivotally secured to the bolt and its rear end projecting beyond the rear of the bolt, resilient means biasing said latch upwardly, a recess in said barrel extension engageable by said latch when the bolt is in battery position, a hammer pivotally mounted in said receiver beneath the bolt and adapted to engage the reai of the firing pin when the bolt is in battery posi tion, a bifurcated follower surrounding said hammer and pivotally mounted to the receiver, said follower adapted to engage said latch when the 

